The present invention relates to construction vehicles, and more particularly to endless tracks or crawlers used to propel such vehicles.
Referring to FIGS. 1–4, tracked construction vehicles 1 are known and basically include a chassis 2 and one or more working tools 3, such as for example, a screed 3 towed from the rear of the chassis 2 with a paving-type construction vehicle 1. Tracked construction vehicles 1 also generally include a pair of wheel trains 4 (one shown) each mounted to a separate lateral side 2a (one shown) of the chassis 2 and two “crawlers” or endless tracks 5 (one shown) each encircling one of the wheel trains 4. Each wheel train 4 typically includes a drive wheel 6, several roller or “bogie” wheels 7 and a take-up wheel 8 (although a second drive wheel may alternatively be provided). Typically, the bogie wheels 7 and the take-up wheels 8 are arranged in laterally spaced-apart pairs that are mounted on common or collinear axles, as best shown in FIG. 3.
The tracks 5 are typically constructed as either a belt of linked together metal plates, typically of low carbon steel (not shown), or as a continuous or endless band or belt of a polymeric material (as depicted), such as natural or synthetic rubber. The polymeric tracks 5 are generally of one-piece construction in the form of a continuous belt 9 of material having a generally ovular or elliptical shape when mounted about a wheel train 4. Each belt 9 has an outer surface 9a which contacts the roadway or other ground surface S on which the paver 1 travels and an inner surface 9b which contacts and slides against the various wheels 6, 7 and 8 of the wheel train 4. A plurality of teeth or lugs 10 project radially inwardly from the belt inner surface 9b and engage with teeth/lugs (not shown) of the drive wheel 6 such that the drive wheel 6 pulls the track 5 to circle about the wheel train 4, the circling track 5 in turn pulling the paver 1 along the ground surface S.
As best shown in FIG. 3, each endless track 5 includes a tread pattern 11 formed in the belt outer surface 9a to increase frictional engagement or “traction” between the track 5 and roadway or other surface S upon which the paver 1 is travelling. Such tread patterns 11 typically include one or more longitudinally-extending or “longitudinal” recesses 12 that extend generally about the entire circumference of the belt 9. Further, the tread pattern 11 includes a plurality of generally transversely-extending or “transverse” recesses 13 which each extend across the width of the belt 9 and to one or both side edges 9c of the belt 9.
It has been generally believed to be necessary to provide known polymeric endless tracks 5 with the above-described transverse recesses 13 so that sufficient traction may be generated between the tracks 5 and a ground surface S to enable the tracks 5 to pull a paving vehicle 1 across or along the surface S. Further, these transverse recesses 13 also provide channels for removal of debris, such as small rocks or stones, that could become trapped in the tread pattern 11 and adversely affect the track functioning. For these reasons, paving vehicle manufactures have generally considered it necessary to provide polymeric-tracked paving vehicles 1 with tracks 5 having transverse recesses 13.